Question

A photocell is illuminated by a small bright source placed 1 m away. When the same source of light is placed $\frac{1}{2}m$ away, the number of electrons emitted by photo cathode would

• A. Decrease by a factor of 2
• B. Increase by a factor of 2
• C. Decrease by a factor of 4
• D. Increase by a factor of 4

Answer 1

The correct option is D

Increase by a factor of 4

Number of photoelectrons $\propto \frac{1}{(Distance{)}^2}$